Some are just clipped into place, and some have a single screw up at the front of the housing, seen from the outside of the shell (near the windsheld). Some late models have a two piece design and the shell comes off separately from the mount body which the compass is mounted into. Just be carefull to take your time and not break it or the drop down doors which are fragile. 02 and older Expeditions have a single screw inside one of the drop down doors.